Blue Holes of the Bahamas

By Rob Palmer

The Bahamas have been, for many years now, synonymous with a
vision of sandy beaches, swaying palm trees, casinos and cool drinks - a tourist's
paradise of almost mythical proportions.

The Bahamas which lie behind the beaches, and beneath them, are rather different. There
are over 700 islands, large and small, in the Bahamas group, and few of these offer much
for the average tourist. Lush, subtropical forests of pine or broad-leaved scrub cover
much of what higher ground there is, saline mangrove flats cover most of the rest, and the
ground itself is karst, often broken and jagged, a bare limestone surface where the only
soils are in potholes, or "banana holes", in between the fretted ridges, or soft
oolitic deposits between the tangled mangrove roots. It is a natural paradise, but not for
the faint of heart. For those who love nature, it is paradise indeed.

Limestone is a rock susceptible to cave development. Bahamian limestone is no
exception. Despite the lack of surface rivers, in the present era, or much in the way of
surface relief at all, the major islands are underlain by extensive cave systems, often
stretching for many kilometres, and which may reach underwater depths in excess of 100
metres. These caves have formed largely as a result of slow dissolution of the rock at the
base of the islands' freshwater lenses, and by the collapse of cavern roofs when the caves
grew too large to support them. This collapse happened more frequently during periods of
low sea level, when much of the Earth's water was frozen into the great glaciers of the
Ice Ages. Where collapse continued to the surface, entrances to the underworld were
formed. As the oceans rose, these caves were filled once again with water, and the
entrances became lakes on the land, or deep, dark openings in the shallow lagoons inside
the fringing barrier reef. These lakes and openings are the Blue Holes of the Bahamas.

These Blue Holes are
scattered throughout the islands, either forming deep, circular cenotes (similar to those
in Yucatan) in the interior, or as a series of more irregular entrances, generally aligned
along one or more large fracture zones that parallel the Tongue of the Ocean and other
abyssal canyons off the eastern coasts of the islands.

The serious exploration of the Andros caves began in the late 1950's, when a Canadian
diver, photographer and cave explorer called George Benjamin took an interest in the
caves. For over 15 years, George catalogued entrances and explored passages inside the
openings, until many of the most obvious caves had been documented. The centrepiece of
this work was the exploration by George and his team of what has become known as
"Benjamin's Blue Hole", in the South Bight of Andros.

In this cave, and in several nearby caves, over a mile of passages were explored and
mapped, and brief excursions made to depths of up to 300 feet. Both Benjamin and Jacques
Cousteau made television films within the system, and Blue Holes became known in the
public world outside the Bahamas for the first time. Erich Von Daniken, in his book
"Chariots of the Gods", speculated that the deep circular inland Holes might be
the launching pads of ancient extra-terrestrial visitors - a somewhat fanciful notion!

Benjamin's explorations
ended in the mid-1970's, shortly after the deaths of some of his diving companions within
the caves, and in the depths of the Tongue of the Ocean. From then, there was little
serious exploration of the Andros Blue Holes until the arrival of British cave divers in
the early 1980's, the one notable exception being a visit by the famous American cave
diver, Sheck Exley, in 1975. Exley, a support diver on Archie's ill-fated dive, and his
companions explored one Blue Hole in the South Bight of Andros, near to Benjamin's Hole,
to a then world-record depth for an underwater cave of 340' (112m).

Meanwhile, on Grand Bahama, American cave divers were exploring the Lucayan Caverns,
discovering over 8 kilometres of passages in what was then the most extensive underwater
cave system in the world. In the mid-80's it became the Lucayan National Park. The Lucayan
Caverns were where biologist Jill Yager discovered a new order of marine life, Remipedia,
a group of crustacean thought to have become extinct over 150 million years ago. Many new
species have been discovered in inland and marine Blue Holes, and similarities to deep sea
environments have been noted.

Under the leadership of Rob Palmer, two expeditions to the north of the Andros in 1981
and 82 resulted in the exploration of Conch Sound Blue Hole to a point 1200 metres from
its entrance, making it at that time the longest submarine cave known in the world. Many
other nearby caves were explored, and a programme of academic research was inaugurated.

During 1983 and 84, the
British team turned its attention to eastern Grand Bahama, discovering the beautiful and
biologically important Zodiac Caverns below Sweeting's Cay, and the deep marine fracture
systems of Big Creek.

In 1985, the youth expedition "Operation Raleigh" visited South Andros, and a
team under Palmer's direction added to the catalogue of known cave sites, working largely
within the forests inland, and discovering deep cave sites along one of the major fracture
lines paralleling the coast. "Stargate", one of the most magnificent of all Blue
Holes, was discovered during this period.

The years 1986 and 1987 saw the first major integrated scientific study of the Andros
Blue Holes. The international Andros Project was extremely successful, contributing much
in the way of original scientific work in the geological and hydrological processes at
work below the islands, and in studies of palaeo-climatic change in the Earth's past. It
also pioneered the use of mixed gas diving techniques within the Blue Holes, using mixed
gas rebreather to reach depths of over 90 metres below the island. More than 40 Blue Holes
were explored for the first time on this expedition, and a programme on the project was
produced for National Geographic's Explorer series.

The 90's have seen work
focus again on Grand Bahama, where scientists and cave divers from the University of
Bristol have been continuing a programme of exploration and research in the Lucayan
Caverns and the Owl Hole System, studying the hydrology and geology of the caves. This
work has contributed considerably to an understanding of water flow and chemistry beneath
the Bahamas and similar carbonate islands. More work has been done on stalagmite dating,
part of an ongoing programme of palaeo-climatic research, and this has unraveled some of
the mysteries of sea level change over the past millennium. Research is now focusing on
the geomicrobiological processes at work within the caves, as studies reveal how important
a role the smallest of all life - bacteria - play a part in the formation of the caves.

The caves have also revealed secrets of the island's more recent past - in 1987, at the
end of the Andros Project, Palmer discovered the skeletons of several Lucayan Indians in a
Blue Hole on South Andros. In 1990, a joint operation with the Bahamas Department of
Archives and the Bahamas Archaeological Team, brought fragments of 16 skeletons to the
surface, which, together with other, more recently discovered artefacts such as a Lucayan
canoe possibly 1000 years old, from Stargate, are still being studied.

To further reveal the frontiers of Blue Hole potential, American diver Jim King made a
mixed gas exploration to nearly 200 metres in Dean's Blue Hole on Long Island in 1992,
showing that Blue Holes may plunge far deeper than previously thought, while Palmer, Dean
and other divers on a Foundation expedition in 1995 explored a new system on Acklins
Island, called the "Ocean's Den", for over 5000 feet (1500m) of passages in a
single 5 day period. There is much more still to be found.

The Blue Holes offer much to exploration and science. They offer the rare chance to go
where no other has ventured before; they offer an enormous potential for important
original scientific research, and they offer a unique potential for education - the chance
to study and learn how to look after a new environment, and how to sustain it for future
generations of explorers and scientists. This is what we wish to share with others. Our
commitment is to conserving this environment, and to sharing discoveries, not just with
scientists, but with ordinary people, with school children and with those who do not have
the opportunity to themselves venture within the caves, is a firm commitment to share
knowledge and adventure with all who wish to join in the exploration and study of the Blue
Holes of the Bahamas.